I think it's more about what you can do with a mod, what limitations you can live with. Regarding Civ 5, the complete lack of a government system (you "research" government types with culture, but what government form is active, at least before Industrial?), the 1UPT (I don't know if this can be changed in a mod), nailing certain nations down as city states no matter what happens, the rather artificial approach to religions, nation-wide happiness, and the fact the mod support somehow seems to be weaker than in Civ 4 in spite of Steam (it's very easy to load several non-compatible mods and you don't even get a warning) makes it "not worth it". That being said, I could actually live with hexagons, having 64bit should make some things much easier, the additional "culture-based" tech trees are nice (if it was only combined with a true Civic system or at least government type system a la Civ 1 - 3 and some interaction with the main tech tree other than just era), City States who can evolve into a full civ if there is a power vacuum could be great, and quantified ressources would be good if it wasn't a ridiculously low amount (I think the designer wanted to have some kind of RPG, considering how small the armies tend to be - OK that should be moddable). For any kind of realism's sake, xUPT is not a good idea for a civ game because the map tiles are too large and the numbers in any unit is unknown, unless you have some kind of "Size Matters". But even then you could do more to prevent Stacks of Doom with Collateral Damage Logistics The earlier Civ games are too limited in their own way. IIRC the first (slightly) moddable civ game was (you could do little more than changing names), was already much better in this regard (including Multimaps), but completely without Culture or Religion, has Culture but no Religion and a silly tech tree structure. Then there are the other Civ-like games, but they offer little additional benefit. If you didn't care for graphics at all (and didn't mind reprogramming a lot of features), Freeciv would be an alternative.